Casting processes for making films, especially water-soluble films and/or films comprising water-soluble film-forming materials, such as polyvinyl alcohol, are known in the art. Such casting processes utilize a solution of a solvent and a film-forming material, such as polyvinyl alcohol, that is deposited and/or flowed onto a casting surface, such as a metal wheel, roller or belt. The solvent is then removed from the solution, for example by drying. Once the solvent is removed from the solution, a film formed from the film-forming material remains on the casting surface. It is known that casting processes for making films are very time intensive as a result of the need to remove the solvent by drying.
An example of a prior art casting process 10 is shown in FIG. 1. A solution 12 comprising a solvent and a film-forming material is deposited onto an endless metal band 14. The endless metal band 14 transports the solution 12 into a dryer 16. As the solution 12 passes through the dryer 16 the solvent is removed from the solution 12 leaving the film-forming material in the form of a film 18 on the endless metal band 14. The film 18 is then removed from the endless metal band 14 and wound into a roll 19.
Non-water soluble films and/or films comprising non-water soluble non-water soluble filament-forming materials, such as polypropylene, polyethylene, and thermotropic polymers (i.e., polymers that form liquid-crystalline melts) have been produced by spinning a web of filaments of such non-water soluble filament-forming materials and then heat pressing the resulting web into a film, oftentimes a porous film. However, such non-water soluble films and/or films comprising non-water soluble filament-forming materials are unsuitable for uses and/or products that require water-soluble films.
Accordingly, there is a need for a process for making films, especially polar solvent-soluble (for example water-soluble) films and/or films that comprise polar solvent-soluble filament-forming materials and/or water-soluble filament-forming materials that avoids the negatives of known film casting processes, especially the slow rate at which a film is made from a cast solution comprising the solvent and the film-forming material and/or filament-forming material.